WO2025111788A1

WO2025111788A1 - Film-type encapsulation of optical devices with a uv-triggered adhesive layer

Info

Publication number: WO2025111788A1
Application number: PCT/CN2023/134660
Authority: WO
Inventors: Fan GAO; Xiao Wen LIN
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2023-11-28
Filing date: 2023-11-28
Publication date: 2025-06-05
Anticipated expiration: 2026-05-28

Abstract

Adhesive articles capable of encapsulating the surface of an optical device include a release liner and a curable adhesive layer disposed on the release liner. The curable adhesive layer includes a poly (meth) acrylate-based matrix, epoxy functional compounds, at least one photoinitiator, and a photo-activated acid generator. The poly (meth) acrylate-based matrix is formed by the photopolymerization of a reaction mixture including a hydroxyl-functional (meth) acrylate, a (meth) acrylate with a heteroalkylene or heteroarylene group, an optional alkyl (meth) acrylate, an epoxy-functional (meth) acrylate, and a photoinitiator. Upon photo-activation and holding at room temperature for 24-48 hours or heating to a temperature of 70-150℃ for 10-60 minutes, the adhesive layer cures to form an encapsulation layer that is optically clear.

Description

FILM-TYPE ENCAPSULATION OF OPTICAL DEVICES WITH A UV-TRIGGERED ADHESIVE LAYER

Summary

Disclosed herein are adhesive articles capable of encapsulation of optical devices, optical articles that contain the adhesive articles, and methods of preparing the optical articles. The adhesive articles are in the form of a film and are UV-triggered.

The disclosure includes adhesive articles. In some embodiments, the adhesive articles comprise a release liner and a curable adhesive layer disposed on the release liner. The curable adhesive layer comprises: a poly (meth) acrylate-based matrix; epoxy functional compounds; at least one photoinitiator; and a photo-activated acid generator. Upon photo-activation and holding at room temperature for 24-48 hours or heating to a temperature of 70-150℃ for 10-60 minutes, the adhesive layer cures to form an encapsulation layer that is optically clear.

Also disclosed are optical articles that include the cured adhesive articles described above. In some embodiments, the optical article comprises an optical device with a major surface and a cured adhesive article disposed on and encapsulating at least a portion of the major surface of the optical device. The cured adhesive article comprises a curable adhesive layer that has been disposed on the major surface of the optical device and cured. The curable adhesive layer comprises: a poly (meth) acrylate-based matrix; epoxy functional compounds; at least one photoinitiator; and a photo-activated acid generator. Upon photo-activation and holding at room temperature for 24-48 hours or heating to a temperature of 70-150℃ for 10-60 minutes, the curable adhesive layer cures to form an encapsulation layer that is optically clear.

Additionally, methods of preparing the above-described optical articles are disclosed. In some embodiments, the method comprises providing an optical device with a major surface, providing an adhesive article comprising a release liner and a curable adhesive layer disposed on the release liner, as described above, disposing the curable adhesive layer of the curable adhesive article on at least a portion of the major surface of the optical device to form a laminated optical device, removing the release liner from the curable adhesive layer, exposing the adhesive layer to UV radiation, and holding the article at room temperature for 24-48 hours or heating to a temperature of 70-150℃ for 10-60 minutes, to cure the curable adhesive layer to form an encapsulated optical device.

Brief Description of the Drawings

The present application may be more completely understood in consideration of the following detailed description of various embodiments of the disclosure in connection with the accompanying drawings.

Figure 1 is a cross sectional view of an article of this disclosure.

Detailed Description

A wide range of optical devices utilize LED display screens. The display screens have a variety of desirable features that includes high gray scale, wide view range, rich colors, and customizable screen shape. The LED display screens use LEDs (light emitting diodes) . Developments in this technology area include the formation of mini-LED and micro-LED displays. The term "mini-LED" is used to describe the latest technology in TV displays that uses a smaller LED chip to produce the same brightness as a larger chip. This miniaturized design allows for finer control of lighting levels, which makes it ideal for use in both home and commercial lighting applications. The term “micro-LED” refers to an emerging flat-panel display technology consisting of arrays of microscopic LEDs forming the individual pixel elements. Compared to widespread LCD technology, micro-LED displays offer better contrast, response times, and energy efficiency. They are also capable of high speed modulation, and have been proposed for chip-to-chip interconnect applications.

These LEDs typically are encapsulated to protect the LED elements. The encapsulation is typically carried out with a curing siloxane-based liquid, so that the liquid can fill the gaps between the LED elements.

There are a number of drawbacks to the use of a curable liquid encapsulant. Liquids are messy and difficult to handle and apply to the LED surface. Additionally, upon curing of the liquid encapsulant it is difficult to produce a uniform encapsulation layer. Therefore, it would be desirable to have more convenient and consistent way to encapsulate an LED surface. One more convenient method would be the use of an encapsulation layer that can be applied as a film-type article and yet give the desirable gap-filling properties of a liquid. Film-type articles are those that, as the name implies are film articles instead of liquids. Examples of film-type articles are transfer tapes. Transfer tapes are free-standing layers of adhesive that are applied and used in film-form. Typically, transfer tapes are handled and used on a release liner.

The use of film-type articles to encapsulate an LED surface provides a wide range of challenges. The film-like article, like the liquid encapsulants, must be able to fill the gaps between the LED elements. The adhesive layer must also bond strongly to the LED surface so as to remain anchored to the surface. The adhesive must have suitable optical properties (such as optical transparency) and must retain these optical properties over time and upon exposure to the elevated temperatures that the LED articles are subject to in their assembly and use.

In this disclosure film-type articles are described that comprise a curable adhesive layer disposed on release liner. The adhesive layer of the adhesive article can be applied to the surface of the LED article and cured to encapsulate the LED surface. The curing of the adhesive layer is UV-triggered, meaning that the adhesive curing is initiated by UV light to form acid catalysts that cure the adhesive layer either with the addition of mild heating or by maintaining the adhesive layer at room temperature for sufficient time for curing. Also disclosed are optical articles with an encapsulated LED surface, and methods of forming such optical articles.

The term “adhesive” as used herein refers to polymeric compositions useful to adhere together two adherends. Examples of adhesives are adhesive layers. These curable adhesive layers are applied in a curable state and then applied to a surface to form a permanent bond to the surface.

The term “ (meth) acrylate” refers to monomeric acrylic or methacrylic esters of alcohols. Acrylate and methacrylate monomers or oligomers are referred to collectively herein as " (meth) acrylates” . Materials referred to as “ (meth) acrylate functional” are materials that contain one or more (meth) acrylate groups. The term (meth) acrylate encompasses (meth) acryl compounds such as acrylic acid and (meth) acrylic acid.

The term “epoxy-functional” refers to a compound that contains at least one oxirane ring. The term epoxy-functional encompasses epoxy functional monomers such as epoxy (meth) acrylates as well as epoxy resins.

The terms “epoxy” and “oxirane” are used interchangeably and refer to an oxirane ring which is a three membered cyclic ether. “Epoxy resin” refers to chemical compounds that contain epoxy groups.

The terms "room temperature" and "ambient temperature" are used interchangeably to mean temperatures in the range of 20℃ to 25℃.

The term “thermally stable” as used herein to refer to films refers to films that do not change optical properties after 1000 hours at 130℃.

The term “adjacent” as used herein when referring to two layers means that the two layers are in proximity with one another with no intervening open space between them. They may be in direct contact with one another (e.g. laminated together) or there may be intervening layers.

The terms “polymer” and “macromolecule” are used herein consistent with their common usage in chemistry. Polymers and macromolecules are composed of many repeated subunits. As used herein, the term “macromolecule” is used to describe a group attached to a monomer that has multiple repeating units. The term “polymer” is used to describe the resultant material formed from a polymerization reaction.

The term “alkyl” refers to a monovalent group that is a radical of an alkane, which is a saturated hydrocarbon. The alkyl can be linear, branched, cyclic, or combinations thereof and typically has 1 to 20 carbon atoms. In some embodiments, the alkyl group contains 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl.

The term “aryl” refers to a monovalent group that is aromatic and carbocyclic. The aryl can have one to five rings that are connected to or fused to the aromatic ring. The other ring structures can be aromatic, non-aromatic, or combinations thereof. Examples of aryl groups include, but are not limited to, phenyl, biphenyl, terphenyl, anthryl, naphthyl, acenaphthyl, anthraquinonyl, phenanthryl, anthracenyl, pyrenyl, perylenyl, and fluorenyl.

The term “alkylene” refers to a divalent group that is a radical of an alkane. The alkylene can be straight-chained, branched, cyclic, or combinations thereof. The alkylene often has 1 to 20 carbon atoms. In some embodiments, the alkylene contains 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. The radical centers of the alkylene can be on the same carbon atom (i.e., an alkylidene) or on different carbon atoms.

The term “arylene” refers to a divalent group that is carbocyclic and aromatic. The group has one to five rings that are connected, fused, or combinations thereof. The other rings can be aromatic, non-aromatic, or combinations thereof. In some embodiments, the arylene group has up to 5 rings, up to 4 rings, up to 3 rings, up to 2 rings, or one aromatic ring. For example, the arylene group can be phenylene.

The term “heteroalkylene” refers to a divalent group that includes at least two alkylene groups connected by a thio, oxy, or -NR-where R is alkyl. The heteroalkylene can be linear, branched, cyclic, substituted with alkyl groups, or combinations thereof. Some heteroalkylenes are poloxyyalkylenes where the heteroatom is oxygen such as for example, -CH₂CH₂ (OCH₂CH₂) _nOCH₂CH₂-.

The terms “free radically polymerizable” and “ethylenically unsaturated” are used interchangeably and refer to a reactive group which contains a carbon-carbon double bond which is able to be polymerized via a free radical polymerization mechanism.

Unless otherwise indicated, the terms “optically transparent” , and “visible light transmissive” are used interchangeably, and refer to an article, film or adhesive that has a high light transmittance over at least a portion of the visible light spectrum (about 400 to about 700 nm) . Typically, optically transparent articles have a visible light transmittance of at least 90%and a haze of less than 10%.

Unless otherwise indicated, "optically clear" refers to an adhesive or article that has a high light transmittance over at least a portion of the visible light spectrum (about 400 to about 700 nm) , and that exhibits low haze, typically less than about 5%, or even less than about 2%. In some embodiments, optically clear articles exhibit a haze of less than 1%at a thickness of 50 micrometers or even 0.5%at a thickness of 50 micrometers. Typically, optically clear articles have a visible light transmittance of at least 95%, often higher such as 97%, 98%or even 99%or higher.

Disclosed herein are adhesive articles. In some embodiments, the adhesive articles comprise a release liner and a curable adhesive layer disposed on the release liner. The curable adhesive layer comprises a poly (meth) acrylate-based matrix, epoxy functional compounds, at least one photoinitiator, and a photo-activated acid generator. Upon photo-activation and holding at room temperature for 24-48 hours or heating to a temperature of 70-150℃ for 10-60 minutes, the adhesive layer cures to form an encapsulation layer that is optically clear.

The adhesive articles comprise a release liner. Release liners are well known in the adhesive arts and are films from which adhesive compositions or coatings can be readily removed. Exemplary release liners include those prepared from paper (e.g., Kraft paper) or polymeric material (e.g., polyolefins such as polyethylene or polypropylene, ethylene vinyl acetate, polyurethanes, polyesters such as polyethylene terephthalate, and the like, and combinations thereof) . At least some release liners are coated with a layer of a release agent such as a silicone, a fluorosilicone-containing material or a fluorocarbon-containing material. Examples of suitable release liners include RF02N from SKC (easy release liner) and RF12N from SKC (tight release liner) .

The adhesive articles also comprise a curable adhesive layer. The curable adhesive layer comprises a poly (meth) acrylate-based matrix, epoxy functional compounds, at least one photoinitiator, and a photo-activated acid generator. Each of these components is described in detail below.

The curable adhesive layer comprises a poly (meth) acrylate-based matrix. The poly (meth) acrylate-based matrix is formed by the photopolymerization of a reaction mixture comprising: at least one first (meth) acrylate monomer comprising a (meth) acrylate with a hydroxyl-functional alkyl group; at least one second (meth) acrylate monomer comprising a (meth) acrylate with a heteroalkylene group, a heteroarylene group, or a combination of heteroalkylene and heteroarylene groups; an optional third (meth) acrylate monomer comprising an alkyl (meth) acrylate with an alkyl group comprising 4-20 carbon atoms; at least one fourth (meth) acrylate monomer comprising an epoxy-functional (meth) acrylate monomer; and at least one photoinitiator.

The reaction mixture comprises a first (meth) acrylate monomer of general formula 1:
CH₂=CR¹-C (O) -OR²

Formula 1

wherein R¹ is hydrogen or a methyl group, -C (O) -is a carbonyl group C=O, and R² is a hydroxyl-functional alkyl group. Typically, the hydroxyl-functional alkyl group comprises a single hydroxyl group but may contain more than one hydroxyl group. The hydroxyl-functional alkyl group may have a terminal hydroxyl group such that R² is of the general structure: - (CH₂) _a-OH, where a is an integer of 2 or more, or it may have a hydroxyl group located along the alkyl chain. A particularly suitable (meth) acrylate monomer with a hydroxyl-functional alkyl group is 2-HPA (2-hydroxy-propyl acrylate) that has the general formula 1A:
CH₂=CH-C (O) -O-CH₂-CH (OH) -CH₃

Formula 1A

The reaction mixture comprises a second (meth) acrylate monomer of general formula 2:
CH₂=CR¹-C (O) -OR³

Formula 2

wherein R¹ is hydrogen or a methyl group, -C (O) -is a carbonyl group C=O, and R³ is a heteroalkylene group, a heteroarylene group, or a combination of a heteroalkylene and heteroarylene groups. Typically, the heteroatom or heteroatoms are oxygen atoms. In some embodiments, R³ is of the general structure: - (R⁵-O) _c-R⁶, wherein c is an integer of 1 or greater; R⁵ is an alkylene group with 1-5 carbon atoms or arylene group with 6-10 carbon atoms; and R⁶ is an alkyl group with 1-5 carbon atoms or aryl group with 6-10 carbon atoms. In some embodiments, R⁵ is an alkylene group; and R⁶ is an aryl group. Examples of suitable second monomers include phenoxy ethyl (meth) acrylate) , benzyl (meth) acrylate, and tetrahydrofurfuryl (meth) acrylate. A particularly suitable second (meth) acrylate monomer is PHEA (phenoxy ethyl acrylate) where R⁵ is an ethylene group; and R⁶ is a phenyl group.

The reaction mixture may comprise an optional third (meth) acrylate monomer of general formula 3:
CH₂=CR¹-C (O) -OR⁴

Formula 3

wherein R¹ is hydrogen or a methyl group, -C (O) -is a carbonyl group C=O, and R⁴ is an alkyl group comprising 4-20 carbon atoms. A wide range of alkyl (meth) acrylate monomers are suitable

Suitable alkyl (meth) acrylate monomers include, but are not limited to, those selected from the group consisting of the esters of acrylic acid or methacrylic acid with non-tertiary alkyl alcohols such as 1-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 1-methyl-1-butanol, 1-methyl-1-pentanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 2-ethyl-1-butanol, 2-ethyl-1-hexanol, 3, 5, 5-trimethyl-1-hexanol, 3-heptanol, 2-octanol, 1-decanol, 1-dodecanol, and the like, and mixtures thereof. Such monomeric acrylic or methacrylic esters are known in the art and are commercially available. In some embodiments, the first (meth) acrylate monomer comprises alkyl groups comprising 8-18 carbon atoms. Examples of particularly suitable alkyl acrylate monomers are isooctyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, isobutyl acrylate, dodecyl acrylate and mixtures thereof.

The reaction mixture comprises a fourth (meth) acrylate monomer of general formula 4:
CH₂=CR¹-C (O) -OR⁷

Formula 4

wherein R¹ is hydrogen or a methyl group, and R⁷ is an epoxy-functional group of the general formula - (CH₂) _d-A, where d is an integer of 1 or greater, and A is an oxirane ring. Typically, d is 3 or less. Particularly suitable fifth monomers are those where d is 1, glycidyl acrylate (GA) and glycidyl methacrylate (GMA) .

The reaction mixture also comprises at least one photoinitiator. Photoinitiators are initiators that are activated by light, generally ultraviolet (UV) light, although other light sources could be used with the appropriate choice of initiator, such as visible light initiators, infrared light initiators, and the like to form free radicals to initiate free radical polymerization. Typically, UV photoinitiators are used as the initiator. Photoinitiators are well understood by one of skill in the art of (meth) acrylate polymerization. Examples of suitable free radical photoinitiators include IRGACURE 4265, IRGACURE 184, IRGACURE 651, IRGACURE 1173, IRGACURE 819, IRGACURE TPO, IRGACURE TPO-L, commercially available from BASF, Charlotte, NC.

The curable adhesive layer also comprises at least one epoxy-functional compound. A wide range of epoxy compounds are suitable. Typically, polyfunctional, that is to say difunctional or higher functional, epoxy resins are used so as to provide crosslinking.

Suitable epoxy resins include diglycidyl ether-based epoxy resins and alicyclic epoxy resins such as diepoxy acetals, diepoxy adipates, diepoxy carboxylates, and dicyclopentadiene-based epoxy resins; isocyanurate derivative epoxy resins such as triglycidyl isocyanurate; bisphenol A epoxy resins, bisphenol F epoxy resins, phenol novolak epoxy resins, cresol novolak epoxy resins, naphthalene epoxy resins, biphenyl epoxy resins, aralkyl epoxy resins and biphenylaralkyl epoxy resins. Two or more of these resins may also be used in combination.

In some embodiments, the polyfunctional epoxy resin is of general Formula 5:
W (-T- (-CH₂CH₂-O-) ) _r

Formula 5

wherein W is a single bond or an r valent atom or aliphatic group, each T independently comprises an aliphatic linking group comprising an alkylene group, a heteroalkylene group, or a combination of alkylene and heteroalkylene groups, wherein the alkylene and heteroalkylene groups are linked by ether linkages, ester linkages, or a combination thereof, - (-CH₂CH₂-O-) is an oxirane ring, and r is an integer of 2 or greater.

Among the particularly suitable polyfunctional epoxy resins are difunctional epoxy resins. In some embodiments, the difunctional epoxy resin comprises Formula 6:
(-O-CH₂-CH₂-) -CH₂- (O-V-O-) -CH₂- (-CH₂CH₂-O-)

Formula 6

where V comprises an alkylene group, a heteroalkylene group, or a combination of alkylene and heteroalkylene groups, wherein the alkylene and heteroalkylene groups are linked by ether linkages, ester linkages, or a combination thereof, and - (-CH₂CH₂-O-) is an oxirane ring. Particularly suitable epoxy resins are DGEBA (diglycidyl ether of Bisphenol-A) resins such as EPON 828 from HEXION and NPES-901 from Nan Ya. In some embodiments, the curable adhesive layer comprises at least one difunctional epoxy resin.

The curable adhesive layer also comprises at least one photo-activated acid generator. The photo-activated acid generator generates an acid upon exposure to actinic radiation. The generated acid functions as a catalyst to catalyze the curing of the curable adhesive layer. Photoacid generators are generally known, and reference may be made to K. Dietliker, Chemistry and Technology of UV and EB Formulation for Coatings, Inks and Paints, vol. III, SITA Technology Ltd., London, 1991. Further reference may be made to Crivello J.V. (1984) Cationic polymerization -Iodonium and sulfonium salt photoinitiators. In: Initiators -Poly-Reactions -Optical Activity. Advances in Polymer Science, vol 62. Springer, Berlin, Heidelberg. “Actinic radiation” means photochemically active radiation and particle beams, including electromagnetic radiation, for example, microwaves, infrared radiation, visible light, ultraviolet light, X-rays, and gamma-rays. In some embodiments, actinic radiation having a wavelength between about 200 and about 800 nm may be used and particularly actinic radiation having a wavelength between about 200 and about 400 nm.

Examples of suitable photo-activated acid generators include, but are not limited to: iodonium and sulfonium salts, such as diaryliodonium, triarylsulfonium, dialkylphenacylsulfonium and dialkyl-4-hydroxyphenylsulfonium salts.

Useful iodonium salt photoacid generators include bis (4-t-butylphenyl) iodonium hexafluoroantimonate (FP5034 from Hampford Research Inc., Stratford, CT) , bis (4-tert-butylphenyl) iodonium hexafluorophosphate (FP5035 from Hampford Research Inc., Stratford, CT) , (4-methoxyphenyl) phenyl iodonium triflate, bis (4-tert-butylphenyl) iodonium camphorsulfonate, bis (4-tert-butylphenyl) iodonium hexafluoroantimonate, bis (4-tert- butylphenyl) iodonium hexafluorophosphate, bis (4-tert-butylphenyl) iodonium tetraphenylborate, bis (4-tert-butylphenyl) iodonium tosylate, bis (4-tert-butylphenyl) iodonium triflate, (4-octyloxyphenyl) phenyl iodonium hexafluorophosphate (available as FP5384 from Hampford Research Inc., Stratford, CT) , (4-octyloxyphenyl) phenyl iodonium hexafluoroantimonate (available as FP5386 from Hampford Research Inc., Stratford, CT) , (4-isopropylphenyl) (4-methylphenyl) iodonium tetrakis (pentafluorophenyl) borate (available as RHODORSIL 2074 from Bluestar Silicones, East Brunswick, NJ) , bis (4-methylphenyl) iodonium hexafluorophosphate (available as OMNICAT 440 from IGM Resins Bartlett, IL) , and 4- (2-hydroxy-1-tetradecycloxy) phenyl] phenyl iodonium hexafluoroantimonate.

Useful sulfonium salt photoacid generators include diphenyl (4-phenylthio) phenyl sulfonium hexafluorophosphate, bis (4-diphenylsulfonium phenyl) sulfide bis- (hexafluorophosphate) , diphenyl (4-phenylthio) phenyl sulfonium hexafluoroantimonate, bis (4-diphenylsulfonium phenyl) sulfide bis- (hexafluoroantimonate) , and blends of these triarylsulfonium salts available from Synasia, Metuchen, NJ under the trade designations of UVI-6992 and UVI-6976 for the PF₆ and SbF₆ salts, respectively. Other useful sulfonium salt include triphenyl sulfonium hexafluoroantimonate (available as CT-548 from Chitec Technology Corp. Taipei, Taiwan) , diphenyl (4-phenylthio) phenyl sulfonium hexafluorophosphate available as CPI-100 from San-Apro Limited, Tokyo Japan, and diphenyl (4-phenylthio) phenyl sulfonium [ (R_f) _nPF_6-n] , where R_f is a perfluorinated alkyl group, available as CPI-200 from San-Apro Limited, Tokyo Japan.

Useful dialkylphenacylsulfonium salt photoacid generators have been described by Crivello. J. V. and Lam, J. H. W. in J. Polym. Sci. Polym. Chem. Ed. 17, 2877 (1979) , and an example would be of phenacyltetramethylenesulfonium hexafluorophosphate.

Useful dialkyl-4-hydroxyphenylsulfonium salt photoacid generators have been described by Crivello, J. V. and Lam. J. H. W. in J. Polym. Sci. Polym. Chem. Ed. 18, 1021 (1980) , and an example would be dimethyl-3, 5-dimethyl-4-hydroxyphenylsulfonium hexafluoroantimonate.

Non-limiting examples of anions complexed with any of the onium salts cations described above are: ^-BF₄, ^-AsF₆, ^-PF₆, ^-SbF₆, ^-C (SO₂CF₃) ₃, ^-CH (SO₂CF₃) ₂, ^-B (C₆H₅) ₄, ^-B (C₆F₅) ₄ and ^- [ (R_f) _nPF_6-n] , where R_f is a perfluorinated alkyl group.

In some embodiments, the photo-activated acid generator comprises a diaryliodonium salt, a triarylsulfonium salt, a dialkylphenacylsulfonium salt, a dialkyl-4-hydroxyphenylsulfonium salt, or a combination thereof.

The curable adhesive layer also comprises at least one photoinitiator. Photoinitiators have been described above as components of the reaction mixture used to form the poly (meth) acrylate-based matrix. The photoinitiators comprising the curable adhesive layer may be the same or different from the phonotinitiators used in the reaction mixture. Examples of suitable free radical photoinitiators include IRGACURE 4265, IRGACURE 184, IRGACURE 651, IRGACURE 1173, IRGACURE 819, IRGACURE TPO, IRGACURE TPO-L, commercially available from BASF, Charlotte, NC.

In some embodiments, the curable adhesive layer comprises:

5-35 parts by weight of a poly (meth) acrylate matrix formed by the photopolymerization of a reaction mixture;

2-35 parts by weight of at least one epoxy resin;

0.01-1.0 parts by weight of at least one photoinitiator and

0.005-1.0 parts by weight of at least one photo-activated acid generator.

The reaction mixture comprises:

15-25 parts by weight of at least one first (meth) acrylate monomer comprising a (meth) acrylate with a hydroxyl-functional alkyl group;

50-85 parts by weight of at least one second (meth) acrylate monomer comprising a (meth) acrylate with a heteroalkylene or heteroarylene group;

0-20 parts by weight of an optional third (meth) acrylate monomer comprising an alkyl (meth) acrylate with an alkyl group comprising 4-20 carbon atoms;

1-3 parts by weight of at least one fourth (meth) acrylate monomer comprising an epoxy-functional (meth) acrylate monomer; and

0.01-1.0 parts by weight of at least one photoinitiator.

In addition to the poly (meth) acrylate-based matrix, the curable adhesive layer can have additional optional additives as long as the additives do not adversely affect the optical or thermal stability properties of the curable adhesive layer. Particularly suitable additives are antioxidants. Examples of suitable antioxidants include hindered phenolic antioxidants, alky- aryl phosphite antioxidants, or a combination thereof. Examples of hindered phenolic antioxidants include ADK STAB AO-80 and ADK STAB AO-20 from ADEKA, Hasbrouck Heights, NJ, or IRGANOX 1010 from BASF. Examples of of alkyl-aryl phosphite antioxidants include ADK STAB PEP-36 and ADK STAB PEP-8 from ADEKA, Hasbrouck Heights, NJ and IRGAFOS 168 from BASF. In some embodiments, the curable adhesive layer further comprises at least one antioxidant, in an amount of 0.01-0.2 parts by weight.

As mentioned above, the adhesive articles of this disclosure have a variety of desirable features. The substrate is optically clear and thermally stable, by which it is meant that the substrate maintains optical clarity when aged for 1000 hours at 130℃, as measured by %Transmission, Haze, and b*. Additionally, the curable adhesive layer, upon curing to form an encapsulation layer is thermally stable, maintaining optical clarity when aged for 1000 hours at 130℃, as measured by %Transmission, Haze, and b*. Therefore, the cured adhesive article has optical clarity and maintains optical clarity when aged for 1000 hours at 130℃, as measured by %Transmission, Haze, and b*.

This disclosure also describes optical articles. The optical articles comprise an optical device with a major surface and a cured adhesive article disposed on and encapsulating at least a portion of the major surface of the optical device. The cured adhesive article comprises a curable adhesive layer that has been disposed on the major surface of the optical device and cured. The curable adhesive layer has been described above and comprises a poly (meth) acrylate-based matrix; epoxy functional compounds; at least one photoinitiator; and a photo-activated acid generator, such that upon photo-activation and holding at room temperature for 24-48 hours or heating to a temperature of 70-150℃ for 10-60 minutes, the curable adhesive layer cures to form an encapsulation layer that is optically clear.

A wide range of optical devices can be used to from the optical articles of this disclosure. Examples of suitable optical devices with a major surface include an LED, a mini-LED, or a micro-LED.

The optical articles also comprise a cured adhesive article that is a curable adhesive article that has been cured on at least a portion of the major surface of the optical device. The curable adhesive articles are described in detail above and comprise a curable adhesive layer on a release liner.

As described above, the curable adhesive layer comprises a poly (meth) acrylate-based matrix; epoxy functional compounds; at least one photoinitiator; and a photo-activated acid generator.

The poly (meth) acrylate-based matrix is formed by the photopolymerization of a reaction mixture comprising: at least one first (meth) acrylate monomer comprising a (meth) acrylate with a hydroxyl-functional alkyl group; at least one second (meth) acrylate monomer comprising a (meth) acrylate with a heteroalkylene or heteroarylene group; an optional third (meth) acrylate monomer comprising an alkyl (meth) acrylate with an alkyl group comprising 4-20 carbon atoms; at least one fourth (meth) acrylate monomer comprising an epoxy-functional (meth) acrylate monomer; and at least one photoinitiator. Each of these components is described in detail above.

The epoxy functional compounds, at least one photoinitiator, and a photo-activated acid generator are described in detail above.

Also disclosed are methods of preparing optical articles. The method comprises providing an optical device with a major surface, providing a curable adhesive article comprising a release liner and a curable adhesive layer, disposing the curable adhesive layer of the curable adhesive article on at least a portion of the major surface of the optical device to form a laminated optical device, removing the release liner from the curable adhesive layer, and holding the article at room temperature for 24-48 hours or heating to a temperature of 70-150℃ for 10-60 minutes, to cure the curable adhesive layer to form an encapsulated optical device.

A wide range of optical devices can be used in the methods to from the optical articles of this disclosure. Examples of suitable optical devices with a major surface include an LED, a mini-LED, or a micro-LED.

As described above, the curable adhesive article comprises a curable adhesive layer disposed on a release liner. The curable adhesive layer comprises a poly (meth) acrylate-based matrix; epoxy functional compounds; at least one photoinitiator; and a photo-activated acid generator.

As described above, the curable adhesive layer comprises a poly (meth) acrylate-based matrix formed by the photopolymerization of a reaction mixture comprising: at least one first (meth) acrylate monomer comprising a (meth) acrylate with a hydroxyl-functional alkyl group; at least one second (meth) acrylate monomer comprising a (meth) acrylate with a heteroalkylene or heteroarylene group; an optional third (meth) acrylate monomer comprising an alkyl (meth) acrylate with an alkyl group comprising 4-20 carbon atoms; at least one fourth (meth) acrylate monomer comprising an epoxy-functional (meth) acrylate monomer; and at least one photoinitiator. Each of these components is described in detail above.

The curable adhesive layer further comprises epoxy functional compounds, at least one photoinitiator, and a photo-activated acid generator. Each of these components are described in detail above.

In some embodiments, providing an adhesive article comprises: providing a release liner; preparing a poly (meth) acrylate matrix pre-cursor reaction mixture; photopolymerizing the poly (meth) acrylate matrix pre-cursor reaction mixture to form a syrup; adding components to the syrup and mixing to form a curable adhesive composition; and disposing the curable adhesive composition on the release liner to form a curable adhesive layer.

The poly (meth) acrylate matrix pre-cursor reaction mixture comprising: at least one first (meth) acrylate monomer comprising a (meth) acrylate with a hydroxyl-functional alkyl group; at least one second (meth) acrylate monomer comprising a (meth) acrylate with a heteroalkylene or heteroarylene group; an optional third (meth) acrylate monomer comprising an alkyl (meth) acrylate with an alkyl group comprising 4-20 carbon atoms; at least one fourth (meth) acrylate monomer comprising an epoxy-functional (meth) acrylate monomer; and at least one photoinitiator.

The components added to the syrup comprise at least one epoxy resin, at least one photoinitiator, and a photo-activated acid generator.

An example of an optical article of this disclosure is described in Figure 1. Figure 1 shows a cross sectional view of article 100. Article 100 shows an encapsulated optical article. The optical article includes substrate 120 and LEDs 130. The optical article is encapsulated by the cured adhesive layer 110. These articles and their components are described above.

Examples

These examples are merely for illustrative purposes only and are not meant to be limiting on the scope of the appended claims. All parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight, unless noted otherwise. The following abbreviations are used: nm = nanometers; Pa = Pascals; s = seconds; h = hours; mJ = milliJoules; mW = milliWatts.

Table of Abbreviations

Test Methods

Initial curing test

Samples were exposed to 365nm LED (5000 mJ) and then heated in an oven at 120℃ for 1h. After curing, the tackiness of the surface of the cured adhesive was determined by touching with a fingertip to feel the tackiness.

Aging test

Samples were laminated between two pieces of glass and bubbles were removed in an autoclave by autoclave. Samples were put into 140℃ oven for aging. Optical performances were tested before and after aging using a Hazegard for the haze and transmission measurements and a Konica Minolta 3700d for the b*measurements.

Shrinkage test

Samples were laminated to a piece of aluminum foil and the release liner was removed. The sample was exposed to UV light and then cured at 120℃ for 1h. After curing the foil was observed to determine is curving occurred indicating shrinkage by the adhesive film.

Rheology test

Rheology for the samples before and after curing were tested using a DHR3 from TA Instruments.

Examples 1-3

Sample preparation

Step 1: Preparation of syrup

Three syrups were prepared by mixing the monomers and initiator shown in Table 1. The amounts are in parts by weight. The mixtures were purged with N₂. The mixture was exposed to 365nm UV light, 60mW for 30s.

Table 1

Step 2: Preparation of adhesive film

The additional components shown in Tables 2-4 were mixed with the syrups shown and the mixture was vacuum treated. The resultant adhesive mixture was coated between 2 release liners (Release Liner-1 and Release Liner-2) with a gap of 250 micrometers and then cured under 405nm LED light, with the UV setting of 3 mW 60s, 6 mW 60s and 30 mW 120s.

Table 2: Composition of Example 1 Samples

Table 3: Composition of Example 2 Samples

Table 4: Composition of Example 2 Samples

Step 3: Application and curing method

One of the release liners was removed and the exposed adhesive surface was laminated to the surface of the Substrate. The laminate was exposed to 365nm LED (5000 mJ) light. The second release liner was removed and the laminate article was placed in an oven and heated to full curing.

Step 4: Testing and results

Initial curing test

Samples 1-1 to 1-9 were tested for tackiness after curing using the test method described above. Sample 1-1, 1-2, 1-3, 1-6 still feels very tacky, while Sample 1-4, 1-7 had some tackiness and 1-5, 1-8, 1-9 had almost no tackiness.

Aging test

Samples 1-4 and 1-8 were tested for optical performance before and after aging using the test method described above. The results are shown in Table 5 below.

Table 5: Aging performance

As shown in Table 5, after aging, the transmission, haze and b*are within an acceptable range. Up to 0.45%photoacid did not cause severe yellowing.

Shrinkage test

Sample 2-2 was tested for shrinkage using the test method described above. No curving of the foil after curing was observed, indicating the shrinkage of the adhesive film after curing was very low.

Rheology test

Samples 2-2, 2-3, and 3-1 were tested before curing and after being cured as described. Sample 2-2 curing conditions: 5 mJ UV, 70℃ 1h; Sample 2-3 curing conditions: 5 mJ UV, 150℃ 1h; and Sample 3-1 curing conditions: 5 mJ UV, 70℃ 1h. The pre-cured adhesive films had a high tan δ and low modulus, indicating good gap filling capability. After curing the Tg and modulus increased significantly. For samples 2-2 and 3-1, the higher photoacid content resulted in better curing. After curing, the high temperature modulus is greater than 3x10⁵Pa. Sample 2-3 having less photoacid, even after curing at a higher temperature, the high temperature modulus is lower than 3x10⁵Pa.

Claims

An adhesive article comprising:

a release liner; and

a curable adhesive layer disposed on the release liner, wherein the curable adhesive layer comprises:

a poly (meth) acrylate-based matrix;

epoxy functional compounds;

at least one photoinitiator; and

a photo-activated acid generator, such that upon photo-activation and holding at room temperature for 24-48 hours or heating to a temperature of 70-150℃ for 10-60 minutes, the adhesive layer cures to form an encapsulation layer that is optically clear.
The adhesive article of claim 1, wherein the poly (meth) acrylate-based matrix is formed by the photopolymerization of a reaction mixture comprising:

at least one first (meth) acrylate monomer comprising a (meth) acrylate with a hydroxyl-functional alkyl group;

at least one second (meth) acrylate monomer comprising a (meth) acrylate with a heteroalkylene or heteroarylene group;

an optional third (meth) acrylate monomer comprising an alkyl (meth) acrylate with an alkyl group comprising 4-20 carbon atoms;

at least one fourth (meth) acrylate monomer comprising an epoxy-functional (meth) acrylate monomer; and

at least one photoinitiator.
The adhesive article of claim 1, wherein the epoxy-functional compounds comprise at least one difunctional epoxy resin.
The adhesive article of claim 1, wherein the photo-activated acid generator comprises a diaryliodonium salt, a triarylsulfonium salt, a dialkylphenacylsulfonium salt, a dialkyl-4-hydroxyphenylsulfonium salt, or a combination thereof.
The adhesive article of claim 1, wherein the curable adhesive layer, upon curing to form an encapsulation layer is thermally stable, maintaining optical clarity when aged for 1000 hours at 130℃, as measured by %Transmission, Haze, and b*.
The adhesive article of claim 1, wherein the curable adhesive layer further comprises at least one additive selected from hindered phenolic antioxidants, alky-aryl phosphite antioxidants, or a combination thereof.
The adhesive article of claim 1, wherein the curable adhesive layer comprises:

5-35 parts by weight of a poly (meth) acrylate matrix formed by the photopolymerization of 15-25 parts by weight of at least one first (meth) acrylate monomer comprising a (meth) acrylate with a hydroxyl-functional alkyl group;

50-85 parts by weight of at least one second (meth) acrylate monomer comprising a (meth) acrylate with a heteroalkylene or heteroarylene group;

0-20 parts by weight of an optional third (meth) acrylate monomer comprising an alkyl (meth) acrylate with an alkyl group comprising 4-20 carbon atoms;

1-3 parts by weight of at least one fourth (meth) acrylate monomer comprising an epoxy-functional (meth) acrylate monomer; and

0.01-1.0 parts by weight of at least one photoinitiator and

2-35 parts by weight of at least one epoxy resin;

0.01-1.0 parts by weight of at least one photoinitiator and

0.005-1.0 parts by weight of at least one photo-activated acid generator.
The adhesive article of claim 7, wherein the curable adhesive layer further comprises:

0.01-0.2 parts by weight of at least one antioxidant.
An optical article comprising:

an optical device with a major surface; and

a cured adhesive article disposed on and encapsulating at least a portion of the major surface of the optical device, wherein the cured adhesive article comprises a curable adhesive layer that has been disposed on the major surface of the optical device and cured, the curable adhesive layer comprising:

a poly (meth) acrylate-based matrix;

epoxy functional compounds;

at least one photoinitiator; and

a photo-activated acid generator, such that upon photo-activation and holding at room temperature for 24-48 hours or heating to a temperature of 70-150℃ for 10-60 minutes, the curable adhesive layer cures to form an encapsulation layer that is optically clear.
The optical article of claim 9, wherein the optical device with a major surface comprises an LED. a mini-LED, or a micro-LED.
The optical article of claim 9, wherein the poly (meth) acrylate-based matrix is formed by the photopolymerization of a reaction mixture comprising:

at least one first (meth) acrylate monomer comprising a (meth) acrylate with a hydroxyl-functional alkyl group;

at least one second (meth) acrylate monomer comprising a (meth) acrylate with a heteroalkylene or heteroarylene group;

an optional third (meth) acrylate monomer comprising an alkyl (meth) acrylate with an alkyl group comprising 4-20 carbon atoms;

at least one fourth (meth) acrylate monomer comprising an epoxy-functional (meth) acrylate monomer; and

at least one photoinitiator.
The optical article of claim 9, wherein the curable adhesive layer, upon curing to form an encapsulation layer is thermally stable, maintaining optical clarity when aged for 1000 hours at 130℃, as measured by %Transmission, Haze, and b*.
The optical article of claim 9, wherein the curable adhesive layer comprises:

5-35 parts by weight of a poly (meth) acrylate matrix formed by the photopolymerization of 15-25 parts by weight of at least one first (meth) acrylate monomer comprising a (meth) acrylate with a hydroxyl-functional alkyl group;

50-85 parts by weight of at least one second (meth) acrylate monomer comprising a (meth) acrylate with a heteroalkylene or heteroarylene group;

0-20 parts by weight of an optional third (meth) acrylate monomer comprising an alkyl (meth) acrylate with an alkyl group comprising 4-20 carbon atoms;

1-3 parts by weight of at least one fourth (meth) acrylate monomer comprising an epoxy-functional (meth) acrylate monomer; and

0.01-1.0 parts by weight of at least one photoinitiator and

2-35 parts by weight of at least one epoxy resin;

0.01-1.0 parts by weight of at least one photoinitiator and

0.005-1.0 parts by weight of at least one photo-activated acid generator.
The optical article of claim 9, wherein the curable adhesive layer further comprises at least one antioxidant.
A method of preparing an optical article comprising:

providing an optical device with a major surface;

providing an adhesive article comprising:

a release liner; and

a curable adhesive layer disposed on the release liner, wherein the curable adhesive layer comprises:

a poly (meth) acrylate-based matrix;

at least one epoxy resin;

at least one photoinitiator; and

a photo-activated acid generator, such that upon photo-activation and holding at room temperature for 24-48 hours or heating to a temperature of 70-150℃ for 10-60 minutes, the adhesive layer cures to form an encapsulation layer that is optically clear;

disposing the curable adhesive layer of the curable adhesive article on at least a portion of the major surface of the optical device to form a laminated optical device;

removing the release liner from the curable adhesive layer;

exposing the adhesive layer to UV radiation; and

holding the article at room temperature for 24-48 hours or heating to a temperature of 70-150℃ for 10-60 minutes, to cure the curable adhesive layer to form an encapsulated optical device.
The method of claim 15, wherein the optical device with a major surface comprises an LED, a mini-LED, or a micro-LED.
The method of claim 15, wherein the curable adhesive layer comprises a poly (meth) acrylate-based matrix formed by the photopolymerization of a reaction mixture comprising:

at least one first (meth) acrylate monomer comprising an alkyl (meth) acrylate with an alkyl group comprising 4-20 carbon atoms;

at least one second (meth) acrylate monomer comprising a (meth) acrylate with a hydroxyl-functonal alkyl group;

an optional third (meth) acrylate monomer comprising a (meth) acrylate with a heteroalkylene or heteroarylene group;

at least one fourth (meth) acrylate monomer comprising an epoxy-functional (meth) acrylate monomer; and

at least one photoinitiator.
The method of claim 15, wherein the curable adhesive layer, upon curing to form an encapsulation layer is thermally stable, maintaining optical clarity when aged for 1000 hours at 130℃, as measured by %Transmission, Haze, and b*.
The method of claim 15, wherein providing an adhesive article comprises:

providing a release liner;

preparing a poly (meth) acrylate matrix pre-cursor reaction mixture comprising:

at least one first (meth) acrylate monomer comprising a (meth) acrylate with a hydroxyl-functional alkyl group;

at least one second (meth) acrylate monomer comprising a (meth) acrylate with a heteroalkylene or heteroarylene group;

an optional third (meth) acrylate monomer comprising an alkyl (meth) acrylate with an alkyl group comprising 4-20 carbon atoms;

at least one fourth (meth) acrylate monomer comprising an epoxy-functional (meth) acrylate monomer; and

at least one photoinitiator;

photopolymerizing the poly (meth) acrylate matrix pre-cursor reaction mixture to form a syrup; adding components to the syrup and mixing to form a curable adhesive composition, the components comprising:

at least one epoxy resin;

at least one photoinitiator; and

a photo-activated acid generator;

disposing the curable adhesive composition on the release liner to form a curable adhesive layer.